1. Field of the Invention
The invention relates to a fluorescence material and an illumination element. More particularly, the invention relates to a fluorescence material and a white light illumination element in which the fluorescence material is applied.
2. Description of Related Art
A light emitting diode (LEDs) has various advantages, such as long service life, small volume, high shock resistance, low heat output, and low power consumption, and therefore the LED has been widely applied in indicators or light sources for household appliances and various equipment. In recent years, the LED has been developed toward multicolor and high luminance, and thus the application scope of the LED has been expanded to large outdoor billboards, traffic signal lights, and the like. Recently, light output efficiency of the LED is continuously increasing, such that conventional fluorescent lamps and incandescent bulbs tend to be gradually replaced by a white LED device when the white LED device serves as a light source of a scanner, a backlight source of a liquid crystal display screen, an illuminator, and so forth.
The conventional white LED device can be mainly divided into the following categories:
1. The white light is generated by a red LED chip, a blue LED chip, and a green LED chip. Since a plurality of single-colored LED chips are required in this type of white LED device, the production costs are rather high, and the design of the driving circuit is relatively complicated.
2. The white light is generated by a blue LED chip together with yellow fluorescence powder. The production costs of said white LED device are relatively low. However, the common yellow fluorescence powder includes the yttrium aluminum garnet (YAG) fluorescence powder, and the YAG fluorescence powder applied to the white LED device often has unfavorable color rendering property.
3. The white light is generated by an LED chip together with red fluorescence powder and yellow-green fluorescence powder. In the patent publication no. W002/11173 to ORSAM, the yellow-green fluorescence powder refers to the sulfide-containing fluorescence powder. In this case, the white LED device can have favorable color rendering property. Nonetheless, the sulfide-containing fluorescence powder is very much likely to react with moisture in the air, thus resulting in poor stability and deterioration of the quality of the white LED device.